1. Field of the Invention
The present invention relates to an IC memory card preventing unlawful copying of information such as programs or data stored in the IC memory card onto other media.
2. Description of the Related Art
It is a serious problem for suppliers of software to take effective counter-measures against unlawful copying. Software suppliers have not been able to take positive countermeasures against unlawful copying since there is a risk of adversely affecting the service provided for legitimate users because of such factors as:
(1) copying to a RAM disk or a hard disk is needed since, otherwise, access speed is low; and
(2) backup copies are necessary since access reliability is low, that is, since a multiplicity of read errors or write errors can occur at the time of reading and writing.
On the other hand, IC memory cards that include a RAM or ROM, i.e., a semiconductor memory IC, exhibit a significantly faster access speed than hard disks, and, furthermore, they show excellent access reliability with respect to the same. Thus, even if positive countermeasures against unlawful copying are taken in an IC memory card in which software is stored, it is considered that no problems are likely to arise for legitimate users.
Consequently, the provision of an IC memory card in which effective countermeasures against unlawful copying can be easily taken would represent a great step forward facilitating the wide use of IC cards as an alternative to the conventional floppy disks which can easily be copied unlawfully.
FIG. 1 is a block diagram illustrating the basic internal structure of a conventional IC memory card published in "IC Memory Card Guide Line" published by the Personal Computer Committee, Japan Electronics Industry Association, in September 1986. Referring to this drawing, a memory chip portion 3 generally comprises a plurality of RAM or ROM chips (see FIG. 2); (however, in the case of the RAM chips, an internal power source needs to be provided). An interface connector 1 is a connector for establishing connection with a peripheral equipment. A lower address bus 6 and data bus 7 are directly connected to each of the memory chips in the memory chip portion 3 from the interface connector 1. A control bus 4 and an upper address bus or line 5 are connected to a chip select circuit 2 for selecting a designated memory chip in the memory chip portion 3 from the interface connector 1. The control bus 4 is further connected to each of the memory chips in the memory chip portion 3 from the chip select circuit 2. In this state, the upper address is an address for determining which memory chip in the memory chip portion 3 is selected, while the lower address is an address in each of the memory chips. An external power source line 8 which may be connected to a power source (omitted from illustration) disposed outside the IC memory card extends from the interface connector 1 to the memory chip portion 3 and the chip select circuit 2, respectively.
FIG. 2 is a block diagram which in further detail illustrates the memory chip portion 3 and the chip select circuit 2 of the block diagram shown in FIG. 1. In this drawing, the same or equivalent parts shown in FIG. 1 are given the same reference numerals. Referring to this drawing, the chip select circuit 2 is composed of, for example, a general purpose gate IC "74HCl38", while the memory chip portion 3 comprises, for example, two ROM chips 31 and 32, each of which has a storing capacity of 32K bytes. A card enable control line (CE) 41 for selecting a specific IC memory card extending from outside the IC memory card is connected to the chip select circuit 2. Chip select control lines (CS1 and CS2) 43 and 44 connect this chip select circuit 2 and the ROM chips 31 and 32, respectively. Output enable control lines (OE) 42 extending from outside the IC memory card for the purpose of controlling data reading are further connected to each of the ROM chips 31 and 32. In the case of FIG. 2, an upper address signal for the upper address line 5 comprises one bit which corresponds to the most-significant address A15 (the number of bits are determined by the number of memory chips which form the memory chip portion). The lower address signal for the lower address bus 6 comprises 15 bits (since the memory capacity of the memory chip is 32K bytes) which correspond to bit A0 from the lower address to bit A14 of the upper address. Furthermore, the data signal for two way data bus 7 comprises, for example, 8 bits which correspond to data D.sub.0 to D.sub.7. In FIG. 2, in order to simplify the description, although the memory chip portion 3 comprises two ROM chips 31 and 32, the same is generally formed by a greater number of memory elements. In that case, the basic operation is not changed, but the number of bits in the upper address line 5, and the number of the chip select control lines 43 and 44 from the chip select circuit 2 are increased.
Since conventional IC cards are formed as described above, a problem arises that the software stored in the IC memory card can be easily read out and copied to another floppy disk, hard disk, or IC card. Therefore, the thus-copied software can be easily executed not only by IC memory cards but also by a variety of media into which it has been unlawfully copied.